How was ʿAlī influential?

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ʿAlī, Muhammad’s cousin and son-in-law, was the fourth caliph and first imam (in Shiʿism) of the Muslim ummah (community). A faction of the ummah asserted that he and his descendants (known as Ahl al-Bayt) were the only rightful successors to Muhammad. This faction is known as the Shiʿah, short for shīʿat ʿAlī (”ʿAlī’s faction”).